白蜡吉丁啮小蜂生物学特性研究

通过林间调查与室内饲养相结合的方法,对白蜡吉丁啮小蜂（Tetrastichus planipennisiYang）的生物学特性进行了初步研究。结果表明,该寄生蜂在吉林省长春市年发生3-4代,以老熟幼虫在寄主幼虫的蛀道内越冬;不同时期的成蜂性比（♀∶♂）为2.39∶1-5.06∶1,平均为3.04∶1;补充20%蜂蜜水的雌雄成蜂平均寿命分别为16.2±1.24 d和7.00±1.19 d,比取食清水的雌雄成虫分别长6.90 d和1.33 d。平均自然寄生率为35.72%,最高可达76.92%。     

白蜡吉丁啮小蜂蛹期发育起点温度和有效积温的研究

白蜡吉丁啮小蜂是蛀干害虫白蜡窄吉丁的重要寄生性天敌,寄生于寄主幼虫的体内,为人工聚殖和应用于生物防治,在7个温度梯度下观测了白蜡吉丁啮小蜂蛹的发育速率,并应用“最小二乘法”测得该小蜂蛹期的发育起点温度为（16．823±1．381）℃,有效积温为（78．851±0．442）日度。     

北京地区白蜡窄吉丁生物学特性研究

白蜡窄吉丁(Agrilus planipennis Fairmaire)是一种危害白蜡的重要蛀干害虫。该虫在北京大兴地区1a发生1代,以老熟幼虫在韧皮部与木质部之间的边材坑道内越冬。4月上旬开始化蛹,4月中旬为化蛹高峰,4月底成虫开始羽化,5月中旬为羽化高峰。5月下旬成虫开始产卵,6月中旬幼虫孵化,持续到7月上旬孵化结束。     

铁岭地区白蜡窄吉丁发生规律及化防技术研究

白蜡窄吉丁是木犀科白蜡树属树木的毁灭性蛀干害虫,以幼虫在树木的韧皮部、形成层和木质部浅层蛀食危害。通过研究发现,铁岭地区白蜡窄吉丁寄主主要有白蜡、洋白蜡、水曲柳和花曲柳,其中以洋白蜡和水曲柳受害较重。该害虫在铁岭地区,每年发生1代,以不同龄期的幼虫在蛹室或蛀道里越冬。越冬幼虫4月下旬开始危害,5月中下旬进入化蛹高峰,6月上中旬达羽化高峰。6月下旬新孵化的幼虫即开始侵入树干内危害。该害虫自然扩散能力较为低下,具假死性。化学防治可采用树干封闭喷雾法、全树喷雾法、注射法等,其中以全树喷雾和树干封闭喷雾防治效果较好。     

白蜡吉丁柄腹茧蜂雌蜂对不同气味源的嗅觉反应研究

白蜡吉丁柄腹茧蜂Spathius agrili Yang是在天津地区新发现的外寄生于白蜡窄吉丁Agrilus planipennis Fairmaire幼虫的重要天敌,对寄主害虫的控制作用较强,具有良好的生物防治利用前景。为有效利用该天敌,从行为生态学角度研究挥发性气味源在该蜂寻找寄主中的作用,以深入了解其寄主定位机制。结果表明,白蜡吉丁柄腹茧蜂对受害白蜡树叶的趋性显著（p〈0.05）,说明白蜡吉丁柄腹茧蜂对寄主栖境的选择主要利用来自受害白蜡树叶所提供的信息。     

长春地区白蜡吉丁天敌种类与自然寄生率的研究

以长春地区的水曲柳林分为对象,调查白蜡吉丁的自然天敌种类及优势天敌,结果表明：白蜡吉丁卵期优势天敌种类为白蜡吉丁平腹小蜂,寄生率达61．3％;幼虫期优势天敌种类为白蜡吉丁啮小蜂,寄生率为68．6％;蛹期寄生天敌种类一种,为东方副凿姬蜂,寄生率为8．64％。白蜡吉丁产卵的季节分布呈先上升至高峰后再下降的趋势,白蜡吉丁平腹小蜂的季节消长趋势与白蜡吉丁一致,但在时间上滞后于白蜡吉丁产卵的规律。白蜡吉丁平腹小蜂可以作为一种潜在的、可开发的优势天地种类对白蜡吉丁进行生物防治。     

白蛾周氏啮小蜂生物学特性研究

白蛾周氏啮小蜂在秦皇岛 1a发生 7代 ,以老熟幼虫在寄主蛹内越冬 ,群集于寄主蛹内 ,其卵、幼虫、蛹及产卵前均在寄主蛹内度过。成蜂在寄主蛹中羽化后 ,先进行交配 (无重复交配现象 ) ,随后咬一“羽化”孔爬出 ,其余的成蜂个体均从该孔羽化而出。刚羽化的成蜂当天即可产卵寄生。白蛾周氏啮小蜂从卵产入寄主蛹中至成蜂羽化、咬破寄主蛹壳出来这一时期的有效积温和发育起点温度分别是 36 5 .12日度和 6 .14℃ ,这对指导人工繁殖白蛾周氏啮小蜂有着重要作用。白蛾周氏啮小蜂在自然界中可以寄生多种鳞翅目食叶害虫 ,包括美国白蛾、大袋蛾、柳毒蛾、榆毒蛾、国槐尺蛾、杨扇舟蛾和桃剑纹夜蛾等 ,为白蛾周氏啮小蜂自然繁殖 ,在自然界中保持较高的种群数量创造了有利条件。     

迹地吉丁生物学特性研究初报

迹地吉丁(Melanophila acuminata de Geer)在河北承德1a发生2代,以幼虫在木质部内越冬。翌年4月开始活动,4月底至6月越冬代成虫羽化,羽化盛期在5月。7月初第一代幼虫老熟化蛹,7月中旬至8月第一代成虫羽化,盛期在8月上中旬,10月中下旬第二代幼虫开始越冬。     

松阴吉丁生物学特性研究初报

松阴吉丁在河北承德1a发生2代,以幼虫在木质部内越冬。翌年4月开始活动,4月底至6月越冬代成虫羽化,羽化盛期在5月。7月初第2代幼虫老熟化蛹,7月中旬至8月第1代成虫羽化,盛期在8月上中旬,10月中下旬第2代幼虫开始越冬。     

美国白蛾的有效天敌—白蛾周氏啮小蜂

从陕西关中美国白蛾蛹中养出的一种新天敌—白蛾周氏啮小蜂Chouioiacuner具有很高的寄生率,在寄主的幼虫期、蛹期都可寄生。在寄主越冬蛹中的寄生率达83.2％,而且每头寄主蛹的出蜂量多,一般为200头以上,最高达306头,室内人工饲养繁殖也很容易。因此这种啮小蜂为防治美国白蛾很有希望的新蜂种。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。